Generally, in manufacturing semiconductor devices, after all wafer level processes are completed, the semiconductor devices, e.g., integrated circuits, formed on a wafer are inspected to determine whether not the semiconductor devices have required electrical characteristics. In this wafer inspection process, a probe card having a plurality of needle-shaped contactors is used as an inspection jig.
In order to perform the wafer inspection, the probe card and the wafer are aligned such that the contactors are respectively made to face corresponding electrodes on a surface of the wafer and, then, a proper press-contact is made therebetween. After leading ends of the contactors are brought into contact with the wafer surface, the contactors are relatively pressed by a predetermined stroke, i.e., by an overdrive amount. Accordingly, the leading ends of the contactors are respectively brought into press-contact with the corresponding electrodes while breaking a protective film or a contamination film on the wafer surface.
Recently, there is developed a wafer inspection apparatus that allows a wafer to be inspected by one of a plurality of probe cards provided in an inspection chamber while another wafer is being transferred and pressed to or separated from another probe card by a transfer robot or a moving table commonly used for the probe cards. In this wafer inspection apparatus, the single moving table is commonly used for the multiple probe cards and, thus, a configuration of a prober, especially a configuration near a wafer supporter or a chuck top, becomes simple. Further, the integration of probers and the space efficiency are considerably improved (refer to, e.g., Japanese Patent Application Publication No. 2002-22768).
In the above wafer inspection apparatus having a single moving table commonly used for a plurality of probe cards, there is formed a surrounding space sealed between each of the probe cards and the chuck top so apply a vacuum attractive force to the chuck top and/or the probe card. Accordingly the wafer on the chuck top can be brought into press-contact with each of the probe cards by the vacuum. attractive force.
In order to form such a surrounding space, a vertically extensible/contractible cylindrical member, e.g., a bellows is provided around each of the probe cards. Upon completion of the position alignment between the probe card and the wafer, the surrounding space is sucked to vacuum by or in response to the lifting of the chuck top by the moving table. Accordingly, an upward force is applied to the chuck top due to a pressure difference between a pressure (negative pressure) in the surrounding space and an ambient pressure (e.g., atmospheric pressure). Due to the upward force caused from the vacuum attractive force, each contactor of the probe card can be stably in press-contact with each corresponding electrode on the wafer surface by a preset pressure.
In that case, the negative pressure applied between the probe card and the wafer by the vacuum attractive force needs to be precisely coincided with the pressure applied between the probe card and the wafer by a force of lifting the chuck top by the moving table. If not, when the vacuum attractive force replaces the force of lifting the chuck top by the moving table to maintain a press-contact state between the probe card and the wafer, a desired overdrive amount of the press-contact may be not kept properly. Accordingly, the wafer inspection is abnormally performed, or a jig or a workpiece is damaged. In other words, when the vacuum attractive force is weaker than the force of lifting the chuck top, the overdrive amount is decreased and this may result in abnormal wafer inspection. On the other hand, when the vacuum attractive force is stronger than the force of lifting the chuck top, the overdrive amount is increased and this may result in damages of the contactors or the electrodes.
Generally, a deformation amount of a contactor with respect to a load is one of the specifications of the probe card. Therefore, a set value of a load (probe load) to be applied to the probe card with respect to a predetermined overdrive amount, i.e., the amount of deformation of the contactor, may be obtained from the specifications. Thus, in the wafer inspection apparatus, a set value of a negative pressure to be applied to the surrounding space can be theoretically calculated from the set value of the probe load and a shape or an area of the surrounding space.
However, the probe card actually has a design or a manufacturing error and an individual difference (variation). Further, the specifications of the probe card are not satisfied in many cases. Accordingly, a set value (theoretically calculated value) of a negative pressure to be applied between the probe card and the wafer by the vacuum attractive force cannot guarantee a predetermined overdrive amount.